Liquid dispensing device for selectively dispensing a fluid to an animal

ABSTRACT

A liquid dispensing device (100), in particular for watering animals, in particular laboratory animals, such as small rodents or the like, said device (100) comprising a main body (101) which defines a longitudinal cavity (1011) for the passage of watering liquids, said longitudinal cavity (1011) being in communication with the outside through a delivery (1002) and a discharge (1001) for introducing said liquids in said longitudinal cavity (1011) and discharging said liquids from said longitudinal cavity (1011) respectively, a valve body (105) and an annular shape elastic sealing element (120) arranged inside said longitudinal cavity (1011), said valve body (105) comprising a stem with a first portion (106) which extends through said annular sealing element (120) and a flange-shaped head (107), wherein said flange-shaped head (107) is kept pressed against said annular sealing element (120) by means of an elastic thrust element (130), and wherein said stem can switch between a first closing position, in which the flow of said liquid downstream of said annular sealing element (120) is prevented by said annular sealing element (120), and a second opening position, in which the flow of said liquids downstream of said annular sealing element (120) is possible.

CROSS REFERENCE TO RELATED APPLICATION

This application claims benefit under 35 U.S.C. § 371 to internationalapplication No. PCT/IB2019/055143 filed on Jun. 19, 2019, which claimspriority to Italian application No. 102018000006587 filed Jun. 22, 2018,the contents of which are incorporated by reference in their entireties.

TECHNICAL FIELD

The present invention relates to the field of controlled, in particularautomatic, dispensing of liquids. In particular, the present inventionrelates to the field of controlled, in particular automatic, dispensingof liquids, in the field of animal housing, in particular of laboratoryanimals, such as small rodents or similar small animals. In detail, thepresent invention relates to an innovative device for the automaticand/or controlled dispensing of liquids for animals, in particular forlaboratory animals. In further detail, the present invention relates toan innovative device of the aforesaid type adapted to be activated (andtherefore to dispense liquids) by the animals, such as mice, rats andother relatively small laboratory animals and not only.

BACKGROUND ART

Liquid dispensing devices (also commonly known as valves) for theautomatic watering of animals are known in the background art and widelyused. In the context of the present invention, and in particular in thefollowing description, the term “watering” is meant as equivalent toeach of the terms “abbeveramento” and “abbeverazione” both beingcommonly used in the technical field of the present invention.

In particular, the advent and increasing use of individually ventilatedcages has revealed the need for watering devices characterized by highreliability (possibly free from faults and/or improper operation) inorder to prevent, for example, interruptions of supply and/oruncontrolled supply of watering liquids. It is indeed apparent that aninterruption, even temporary, in the supply of watering liquids couldhave irreparable repercussions on health of the animals (and even lead,in the worst case, to the death of the animals themselves), whilst anuncontrolled supply of liquids could result in the flooding of thehousing cage, also in this case with the risk of irreparablerepercussions on animal health.

It has moreover to be noted that animal health is the essentialrequirement to ensure the reliability of the laboratory tests to whichanimals are subjected. Several watering devices for animals have beendeveloped and suggested in the aforementioned field, in particular toguarantee the reliability required by the housing techniques andmethods.

In particular, the latest generation of automatic watering devicesessentially comprise the following common features.

A main body defines a longitudinal cavity in communication with theoutside through an inlet opening and an outlet opening for introducingand discharging the watering liquids, respectively. The hollow bodyhouses the activation mechanism by means of which the animals can openand close the valve, wherein the activation of the valve is achieved bythe animal by moving an elongated cylindrical element made of stainlesssteel, called the needle, which allows the animals to open the valvethereby obtaining a defined amount of water.

Furthermore, the hollow main body houses the sealing mechanism, which isgenerally made by means of an elastomeric gasket against which a portionof the valve called a needle is pressed by means of an element calledthe plunger.

In resting or closing condition, the elastic deformation of the gasketdue to the pressure applied by the head of the needle as a result of thethrust exerted by the plunger prevents the flow of liquids beyond the(downstream of the) elastic gasket (thereby sealing the system), whereason the contrary, a displacement of the needle from the rest positionresults in a loss of contact between the head of the needle and thegasket with consequent flow of liquids (usually water) beyond the(downstream of the) elastic gasket.

Furthermore, in order to allow the needle to return to the resting orclosing position (with consequent interruption of the flow of liquids),the devices of the known type are equipped with some elementsspecifically designed to keep the needle (also named stem) in theresting position (centered with respect to the longitudinal axis of thevalve) and to facilitate its return into said position after having beenmoved by the animal.

Therefore, in practice, according to some of the known solutions, it isthe plunger itself which provides at least in part the elastic thrustnecessary for the correct repositioning of the needle in the resting orclosing position, wherein solutions are known as well which provide, forthe purpose, the use of an additional elastic element located downstreamof the head of the needle; said further median and distal element, alsonamed centering element, helps the needle to return easily to theresting or closing position parallel to the main axis, thereby ensuringthe closing of the device.

The solutions of known type summarized above, although appreciable frommany points of view, such as, for example, constructive simplicity andsubstantially low costs, however, are affected by some disadvantageswhich are currently at least partially unresolved.

A first disadvantage or problem relates to the fact that the risk ofcorpuscles (e.g. resulting from the litter and/or food) gettingdeposited inside the main body is not completely avoided, wherein saidcorpuscles could counteract the return of the needle into the closingposition, wherein with the needle blocked in the opening position thecontinuous flow of liquids can lead, as mentioned above, to flooding thecage or at least excessively moistening or wetting the litter.

In an attempt to overcome the problem of detritus being deposited in themain body and the respective blocking of the needle, so-called“screened” devices, i.e. devices equipped with a protective screenplaced near the outlet opening of the device, have been suggested in therecent past.

However, the screens of the known type, if made of rigid material, whileeffectively counteracting the depositing of detritus, have been found tobe inadmissible or unsuitable for various applications as theyexcessively hinder the switching of the needle from the closing to theopening position and do not facilitate either the return from theopening to the closing position. On the other hand, if made of softermaterials, they often do not effectively counteract the deposit and/oraccumulation of detritus in the main body.

Furthermore, some of the known watering devices, in addition to thedisadvantages mentioned above, are also affected by problems related tothe configuration of the plunger element. This component, in many cases,must provide the necessary elastic force to compress the front of theneedle head against the gasket, in order to ensure the sealing of thevalve, but must also allow the passage of liquids in case of switchingof the needle (from the closing to the opening position) but stillfacilitating or at least not hindering the opposite switching (from theopening to the closing position).

Often, however, the plunger is distorted or damaged due to theprocessing in autoclave to which it is subjected during the steps ofsterilization of the dispensing device, e.g. by effect of the negativepressure which, combined with the high temperatures present in theautoclaves during the decontamination cycles, can deform and alter theelastic properties of these components. In these cases, the replacementof the element is necessary because damaged plunger devices may causeflooding and/or no longer be able to supply the nominal water flow rate.

DESCRIPTION OF THE PRESENT INVENTION

It is therefore the object of the present invention that of overcomingor at least minimizing the drawbacks found in the solutions according tothe prior art, in particular in the liquid dispensing devices withneedle or stem configured valve element.

In particular, it is one of the aims or objects of the present inventionis to find a solution which allows the effective screening of the outletopening of the device, thus avoiding the deposit and/or accumulation ofdebris in the main body of the device itself, in particular withouthindering (or making it too difficult for the animal) the switching ofthe needle or stem from the closing to the opening position, whilstindeed, on the contrary, promoting the opposite switching from theopening to the closing position.

Moreover, it is a further object of the invention to suggest a screeningof the above type that is simple to be produced and implemented, as wellas feasible at low cost.

It is a further object of the present invention to suggest a plungercentering element with improved features, which acts effectively therebyensuring both the necessary pressure on the gasket by the head of theneedle, and at the same time the re-switching of the needle from theopening to the closing position, and without hindering the switching ofthe needle from the closing to the opening position.

In view of the drawbacks affecting the solutions according to the priorart and of the objects summarized above, according to the presentinvention there is suggested a liquid dispensing device, in particularfor watering animals, in particular laboratory animals, such as smallrodents or the like, said device comprising a main body which defines alongitudinal cavity for the passage of watering liquids, saidlongitudinal cavity being in communication with the outside through aninlet and an outlet for introducing said liquids in said longitudinalcavity and discharging said liquids from said longitudinal cavity,respectively, an annular elastic sealing element arranged inside saidlongitudinal cavity, said valve body comprising a stem with a firstportion which extends through said annular sealing element and aflange-shaped head, wherein said flange-shaped head is kept pressedagainst said annular sealing element by means of an elastic thrustelement, and wherein said stem is adapted to be switched between a firstclosing position, in which the flow of said liquids downstream of saidannular sealing element is prevented by said annular sealing element,and a second opening position, in which the flow of said liquidsdownstream of said annular sealing element is possible, wherein saiddispensing device comprises a disc-shaped element made of elastomericmaterial and fixed to said main body at said outlet, wherein saiddisc-shaped element defines a hole substantially coaxial with saidlongitudinal cavity through which said first portion of said stemextends, and wherein the switching of said stem from said first closingposition to said second opening position occurs against the elastic biasexerted by said disc-shaped element, while, on the contrary, theswitching of said stem from said second opening position to said firstclosing position is promoted by the elastic thrust exerted by saiddisc-shaped element.

According to an embodiment, said stem, at said hole of said disc-shapedelement has an outer diameter which substantially corresponds to thediameter of said hole of said disc-shaped element.

According to an embodiment, said disc-shaped element, near said centralhole, comprises a circular-crown-shaped portion with tapered crosssection and increasing thickness from the edge of said central holetowards the outer peripheral edge of said disc-shaped element.

According to an embodiment, the thickness of said circular-crown-shapedportion of said disc-shaped element increases from a minimum thicknessin a uniform manner and substantially proportionally to the radialdistance from said edge of said central hole.

According to an embodiment, said circular-crown-shaped portion has aninner diameter which substantially corresponds to the diameter of saidcentral hole and an outer diameter which is smaller than the maximumdiameter of said disc-shaped element.

According to an embodiment, the disc-shaped element is housed insidesaid main body.

According to an embodiment, said disc-shaped element, at its outerperipheral edge, comprises a substantially toroidal portion.

According to an embodiment, said substantially toroidal portioncomprises a portion defined by the revolution of a semi-circumferencewith respect to a rotation axis perpendicular to said disc-shapedelement.

According to an embodiment, said elastic thrust element comprises anengagement portion which defines a substantially cylindrical engagementcavity in which a second portion of said stem opposite to said firstportion is housed, and wherein said elastic thrust element comprises acircular-crown-shaped base which extends radially from said engagementportion and is placed in contact with said flange-shaped head of saidvalve element on the opposite side with respect to said annular sealingelement.

According to an embodiment, said second portion of said stem is housedin said cylindrical engagement cavity of said thrust element byinterference.

According to an embodiment, said elastic thrust element comprises asubstantially cylindrical side wall which extends from saidcircular-crown-shaped base in the same extension direction as saidengagement portion.

According to an embodiment, said substantially cylindrical cavity isblind or closed at the end of said second portion of said stem.

According to an embodiment, said engagement portion has a substantiallyfrustoconical outer surface narrowing towards the end opposite to saidcircular-crown-shaped base.

According to an embodiment, said substantially cylindrical side wallwhich extends from said circular-crown-shaped base comprises extensionportions the longitudinal extension of which is smaller than the maximumlongitudinal extension of said substantially cylindrical side wall,wherein each of said portions with smaller longitudinal extensiondefines a notch or slot which extends from the free edge of saidsubstantially cylindrical wall opposite to said circular-crown-shapedbase.

According to an embodiment, the thickness of said substantiallycylindrical wall at said notches or slots is greater than the thicknessof the portions of said wall adjacent to said notches or slots.

Further possible embodiments of the present invention are defined in theclaims.

BRIEF DESCRIPTION OF THE FIGURES

Hereinafter, the present invention will be clarified by means of thefollowing detailed description of the embodiments depicted in thedrawings. However, the present invention is not limited to theembodiments described hereinafter and depicted in the drawings; on thecontrary, all the variants of the embodiments described below anddepicted in the drawings which will be apparent to a person skilled inthe art fall within the scope of the invention.

In the drawings:

FIGS. 1 and 2 show a longitudinal section view of a dispensing deviceaccording to an embodiment of the present invention;

FIG. 3 shows longitudinal section views of component parts of adispensing device according to an embodiment of the present invention;

FIG. 4 shows an exploded perspective view of a dispensing deviceaccording to an embodiment of the present invention;

FIGS. 5 and 6 show longitudinal section views of portions of adispensing device according to an embodiment of the present invention;

FIG. 7 shows a perspective view of a plunger element of a dispensingdevice according to an embodiment of the present invention;

FIG. 8 shows a perspective view of a disc-shaped screening element of adispensing device according to an embodiment of the present invention;

FIG. 9 shows a perspective view of a needle-shaped valve element of adispensing device according to an embodiment of the present invention;

FIGS. 10 and 11 each show a section view and a plan view of a diaphragmelement of a dispensing device according to an embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

The present invention applies in particularly advantageous manner to thefield of watering of animals, in particular of laboratory animals, suchas small rodents or the like, this being the reason why the presentinvention will be clarified below with (possible) reference to itsapplication to the watering of animals, in particular of animals of theaforesaid type.

The possible applications of the present invention are however limitedto watering, but on the contrary comprise all those applications inwhich a controlled and/or automatic dispensing of liquids is required.

According to the embodiment depicted in FIGS. 1, 2 and 4, the dispensingdevice 100 according to the present invention comprises a main body 101constituted by a first element 102, an intermediate element 103 and anend element 104 fixed together (substantially assembled and/or partlyscrewed together according to procedures substantially known inthemselves) so as to define a longitudinal cavity 1011 whichcommunicates with the outside through an inlet opening 1002 and anoutlet opening 1001 for introducing liquids into the cavity 1011 anddischarging liquids from the cavity 1011, respectively. A first O-ringtype gasket 111 is placed between the first element 102 and theintermediate element 103, a second O-ring type gasket 110 being placedbetween the intermediate element 103 and the end element 104, the twogaskets 111 and 110 being provided for the purpose of preventing leakageof liquids at the mutual connections between the elements 102, 103 and104. Furthermore, a third O-ring type gasket 160 is arranged in a groovedefined by the outer surface of the first element 102 in order toguarantee the hydraulic sealing between the element 102 (and thereforebetween the device 100) and, for example, a supply pipe (not shown) towhich the device is fixed.

It can be appreciated that the flow of liquids inside the cavity 1011will occur from the inlet opening 1002 to the outlet opening 1001 andtherefore from left to right in FIGS. 1 and 2.

A valve body or element 105, a further O-ring type gasket 120 and anelement 130 also named plunger for reasons which will be apparent inlight of the following description are arranged or housed inside thecavity 1011. The element 130 comprises a side wall 1301, which issubstantially cylindrical (FIG. 7) and is arranged abutting against acircular crown shoulder 1021 defined by the first element 102 so as toact under pressure (by virtue of the elasticity of the element 130 e.g.made of elastomeric material) against a flange 107 (head) of the valveelement 105, wherein accordingly the pressure applied by the element 130on the flange or head 107 results in a pressure applied by the flange orhead 107 on the gasket 120, the gasket 120, with the valve element 105in the position of FIGS. 1 and 2 (resting or closing) being stressed (inpractice, deformed) under the bias of said pressure so as to block theflow of liquids downstream of the gasket 120 itself.

However, according to methods substantially known and therefore notdescribed in detail for the sake of brevity, the element or valve body105 is adapted to be switched from the position in FIGS. 1 and 2 againstthe elastic bias applied by the element 130 as shown by the double arrowin FIGS. 1 and 2, whilst displacements of the element 105 (in practice,misalignments) from the position in FIGS. 1 and 2, result in a reductionin the strain of the gasket 120 (in practice a loss of contact betweenopposing portions of the gasket 120 and the flange or head 107), andtherefore in the possibility for the liquids to flow from the portion ofcavity 1011 upstream of the gasket 120, into the portion downstream ofthe gasket 120 itself to be discharged through the opening 1001. Forexample, the aforesaid switching or displacements of the element 105 maybe caused by thrust actions (or even small bites) applied by smallanimals also in this case in substantially known manners.

Hereafter, further details of component parts of the device according tothe present invention will be described below with reference to FIGS. 7and 9.

In particular, as depicted in FIG. 9, the valve element 105 comprises aneedle or stem-shaped portion, from which the flange or head 107radially extends, whereas a first portion 106 of the stem extendsdownstream of the head 107, while a second portion 108 of the stemextends upstream of the head 107 and therefore on the opposite side ofthe head 107 with respect to the first portion 106. The valve element105 is usually made of stainless steel, whereas according to the presentinvention the element 105 may be made of equivalent and alternativematerials.

Element 130, as depicted in FIG. 7, comprises an engagement portion 131(see the following description) that defines a substantially cylindricalinner cavity 132 (possibly with a blind or closed end portion), and acircular crown shaped portion 133 which extends radially outside saidengagement portion 131. Finally, element 130 comprises a substantiallycylindrical outer wall 1301, which extends from thecircular-crown-shaped base 133 in the same direction as the extension ofportion 131.

Still as depicted, the outer surface of the portion 131 isfrustoconical, with diameter decreasing towards the end (as saidpossibly blind or closed) opposite to the base 133. Furthermore, theside wall 1301 comprises a number of notches or slots 135 arrangedregularly along the development of wall 1301, wherein the thickness ofthe wall 1301 at the notches 135 is greater than that of the portions ofwall 136 adjacent to said notches.

In use, as depicted in FIGS. 1, 2 and 4, the portion 108 of the stem ishoused by interference in the cavity 132 of the element 130, wherein thebase 133 of element 130 is placed abutting (pushed) pushed againstflange or head 107 of the element 105, the portion 106 of the element105 extends through gasket 120. Furthermore, the notches 135 allow thepassage of liquids at the portions 136 with reduced wall thickness 1301,said portions 136 not being in contact, i.e. defining the gaps, with theopposite cylindrical wall defined by the first element 102 of body 101.

Furthermore, it can be appreciated that the aforesaid switching of thevalve element 105 from the resting or closing position of FIGS. 1 and 2in their respective opening positions occur against the elastic biasapplied by the element 130, whereas, on the contrary, the oppositeswitching of element 105 from the opening positions to the resting orclosing position are promoted by the elastic thrust applied by theelement 130.

As anticipated, according to an embodiment, the device according to thepresent invention comprises a screening element in order to prevent thedeposit of detritus inside the cavity 1011, wherein said detritus, iftrapped in the cavity 1011 could compromise the operation of the device100, e.g. by blocking the element 105 in the opening position, therebycausing the continuous and uncontrolled flow of liquids. Said screeningelement is described below with reference to FIGS. 1, 2 and 8.

In FIGS. 1, 2 and 8, reference number 109 identifies a disc-shapedelement which defines a central hole 1091. Near the through-hole 1091,the disc-shaped element 109 comprises a circular-crown-shaped portion1092, the thickness of which increases from a minimum thickness at thehole 1091 to a maximum thickness at a predefined radial distance fromthe center of the hole. In the embodiment shown, said radial distance issmaller than the maximum radius of the disc-shaped element 109, whereinembodiments are possible in which said predefined radial distancesubstantially corresponds to the maximum radius of the disc-shapedelement.

Finally, as shown, the disc-shaped element 109 comprises a substantiallytoroidal peripheral portion, and therefore defined by revolution of asurface at least in part cylindrical with respect to a rotation axisperpendicular to the disc-shaped element 109 itself. In practice, thethickness of the disc-shaped element 109 is maximum at the toroidalportion 1093 and in particular greater than that of both thecircular-crown-shaped portion 1092 and that of the intermediatecircular-crown-shaped portion 1094.

In use, the disc-shaped element 109 is fixed to the main body 101 at theoutlet opening 1001 with the portion 106 of the valve body 105 whichextends through the hole 1091, the diameter of the hole substantiallycoinciding with (or being even smaller than) the outer diameter of theportion 106 at the hole 1091. In particular, according to the embodimentas depicted, the disc-shaped element 109 is housed in the main body 101(in the end element 104), the toroidal portion 1093 being in this casehoused in a corresponding groove defined by the body 101 and/or by theelement 104, the contrast between the groove and the toroidal portion1093 preventing the accidental release of the disc-shaped element 109from the body 101.

Moreover, as depicted, the end element 104 defines a tapered(frustoconical) inner surface 1041 with a diameter increasing towardsthe outlet, to which is a surface 1042 substantially perpendicular tothe longitudinal axis X of the cavity 1011 is connected, while theintermediate portion 1094 (with a substantially uniform thickness) ofthe disc-shaped element 109 is arranged at said surface 1042.

It is therefore apparent from the above that the disc-shaped element109, made possibly at least in part, in particular with at least thecircular-crown-shaped portion of fluid-proof elastomeric material,effectively contrasts the entry of detritus and/or corpuscles intocavity 1011, particularly in view of the fact that the thickness ofdisc-shaped element 109 is minimal at hole 1091, the disc-shaped element109 is therefore flexible at least at the hole 1091, so that it ispossible to choose a diameter of hole 1091 which substantially coincideswith the diameter of the portion of stem 106.

Furthermore, the aforesaid features, i.e. minimum thickness of thedisc-shaped element 109 at the hole 1091 and/or elasticity of thedisc-shaped element (e.g. made of elastomeric material), mean that thedisc-shaped element does not contrast the switching of the stem or pin105 from the closing to the opening position, moreover the edge of hole1091 at least for small movements of the stem 105, remains substantiallyin contact with the stem 105 also during the switching thereof (fromclosing to opening and vice versa from opening to closing), therebyensuring a screening of the cavity 1011 also during said switching.

It has moreover to be noted that the system of plunger-centering(element 130), needle (element 105) and elastic diaphragm (disc-shapedelement 109): ensures the centering of all elements along thelongitudinal axis of the valve (and therefore the coaxiality of theactivation system);

due to the centering of all elements along the longitudinal axis of thevalve, ensures uniformity of the activation force of the valve(switching of the needle 105 according to the methods described above)in all directions;

wherein the uniformity of the activation force of the valve in alldirections allows the valve to deliver the same amount of water when theneedle (element 105) is moved with respect to the closed position; andwherein the elastic diaphragm (element 109) makes the valve responseprogressive in terms of activation force and water flow rate.

In practice, due to the fact that the thickness of circular-crown-shapedportion 1092 varies from a minimum thickness at the edge of the hole1091, the elastic response of the disc-shaped element 109 to theswitching of element 105 increases proportionally to the displacement ofthe needle, wherein respectively greater forces are therefore requiredfor greater displacements to increase the amount of water delivered.

On the contrary, the switching of the stem 105 from the opening to theclosing positions is facilitated by the disc-shaped element 109, whichtherefore during aforesaid switching, acts in synergy with the plunger130.

Further details of the device 100 according to an embodiment of thepresent invention are described below with reference to FIGS. 10, 11 and2.

As depicted, in the embodiment as depicted in FIGS. 10, 11 and 2, thedevice comprises a rear safety filter 140 consisting of astainless-steel mesh with micrometric mesh, co-molded on an elastomericsupport. The filter 140 has the function of blocking possible impuritiespresent in the water distribution circuit of the automatic wateringsystem.

Downstream of the rear safety filter 140 there is a micro-perforateddiaphragm 150 kept in place by the filter itself.

This element or diaphragm 150, equipped with one or more micrometricholes 151, makes it possible to equalize the water flow delivered by thedevice 100. The micro-perforated diaphragm 150 is sized in accordancewith the mesh size of the filter to avoid the risk of clogging.

It has thus been demonstrated by means of the detailed description givenabove of the embodiments of the present invention depicted in thedrawings that the present invention allows to achieve the predeterminedobjects by overcoming the drawbacks affecting the devices according tothe prior art.

In particular, the present invention allows the effective protection(screening) of the cavity 1011 from detritus (by virtue of theinnovative disc-shaped element 109) and/or an effective re-switching ofthe stem 105 from the opening to the closing positions, as well as areliable sealing (with the stem in the closing position) and asatisfactory flow of liquids (with the stem in the opening position) byvirtue of the conformation and/or of the innovative features of theplunger 130.

Although the present invention is explained above by means of a detaileddescription of the embodiments shown in the drawings, the presentinvention is not limited to the embodiments described above and shown inthe drawings. On the contrary, all the modifications and/or variants ofthe embodiments described above and shown in the drawings which willappear obvious and immediate to a person skilled in the art are includedin the scope of the present invention.

For example, wide choice is left to the person skilled in the artregarding the choice of materials for making the components of thedevice according to the present invention.

The scope of the present invention is thus defined by the claims.

The invention claimed is:
 1. A liquid dispensing device, for selectivelydispensing water to an animal, said device comprising: a main body whichdefines a longitudinal cavity for the passage of watering liquids, saidlongitudinal cavity being in communication with an inlet for introducingsaid liquids in said longitudinal cavity and an outlet for dischargingsaid liquids from said longitudinal cavity, a valve body and an annularelastic sealing element arranged inside said longitudinal cavity, saidvalve body comprising a stem with a first portion which extends throughsaid annular sealing element and a flange-shaped head, wherein saidflange-shaped head is retained pressed against said annular sealingelement by an elastic thrust element, and wherein said stem is adaptedto be switched between a first closing position, in which the flow ofsaid liquids downstream of said annular sealing element is prevented bysaid annular sealing element, and a second opening position, in whichthe flow of said liquids downstream of said annular sealing element ispossible; and a disc-shaped element made of elastomeric material fixedto said main body at said outlet, wherein said disc-shaped elementdefines a central hole substantially coaxial with said longitudinalcavity through which said first portion of said stem extends, andwherein the switching of said stem from said first closing position tosaid second opening position occurs against an elastic bias exerted bysaid disc-shaped element, while, on the contrary, the switching of saidstem from said second opening position to said first closing position ispromoted by die elastic thrust exerted by said disc-shaped element,wherein said disc-shaped element, near said central hole, comprises aninner portion with a tapered cross-section that increase in thicknessfrom an edge of said central hole towards an outer peripheral edge ofsaid disc-shaped element, wherein the thickness of said inner portion ofsaid disc-shaped element increases from a minimum thickness in a uniformmanner and substantially proportionally in a radial direction from theedge of the central hole towards the outer peripheral edge.
 2. Thedispensing device according to claim 1, wherein at least said innerportion is made of fluid-proof elastomeric material.
 3. The dispensingdevice according to claim 1, wherein said stem, at said hole of saiddisc-shaped element has an outer diameter which substantiallycorresponds to the diameter of said hole of said disc-shaped element. 4.The dispensing device according to claim 1, wherein said inner portionof the disc-shaped element has an inner diameter which substantiallycorresponds to a diameter of said central hole and an outer diameterwhich is smaller than a maximum diameter of said disc-shaped element. 5.The dispensing device according to claim 1, wherein said disc-shapedelement is housed inside said main body.
 6. The dispensing deviceaccording to claim 5, wherein said disc-shaped element, at its outerperipheral edge, comprises a substantially toroidal portion.
 7. Thedispensing device according to claim 6, wherein said substantiallytoroidal portion comprises a curved portion with respect to a rotationaxis perpendicular to said disc-shaped element.
 8. The dispensing deviceaccording to claim 1, wherein said elastic thrust element comprises anengagement portion which defines a substantially cylindricalstem-engagement cavity, in which a second portion of said stem oppositeto said first portion is housed, and wherein said elastic thrust elementcomprises a circular base which extends radially from said engagementportion and is placed in contact with said flange-shaped head of saidvalve body on an opposite side with respect to said annular sealingelement such that the flange-shaped head is positioned between thecircular base and the annular sealing element.
 9. The dispensing deviceaccording to claim 8, wherein said second portion of said stem is housedin said cylindrical engagement cavity of said thrust element.
 10. Thedispensing device according to claim 8, wherein said elastic thrustelement comprises a substantially cylindrical side wall which extendsfrom periphery of said circular base in a same direction and coaxialwith said engagement portion.
 11. The dispensing device according toclaim 8, wherein said substantially cylindrical cavity is blind at theend of said second portion of said stem.
 12. The dispensing deviceaccording to claim 8, wherein said engagement portion has asubstantially frustoconical outer surface narrowing towards an endopposite to said circular base.
 13. The dispensing device according toclaim 10, wherein said substantially cylindrical side wall which extendsfrom said circular base has a first height in a longitudinal direction,the substantially cylindrical side wall including a plurality ofspaced-apart, outwardly extending portions having a second height in thelongitudinal direction that is less than the first height of saidsubstantially cylindrical side wall, and wherein adjacent pairs of saidplurality of outwardly extending portions define a notch or slottherebetween and which extends the first height in the longitudinaldirection of said substantially cylindrical side wall.
 14. Thedispensing device according to claim 13, wherein a thickness of saidsubstantially cylindrical wall at said plurality of outwardly extendingportions is greater than the thickness of the side wall at the adjacentnotches or slots.